substr

SUBSTR Extract a substring out of a string.

   SUBSTR(STRING, OFFSET, LENGTH) extracts a substring out of STRING with
   given LENGTH starting at the given OFFSET.  First character is at offset
   0.  If OFFSET is negative, starts that far from the end of the string.
   If LENGTH is omitted, returns everything to the end of the string.  If
   LENGTH is negative, removes that many characters from the end of the
   string.

   SUBSTR(STRING, OFFSET, LENGTH, REPLACEMENT) will not return the
   substring as specified by STRING, OFFSET, and LENGTH (see above) but
   rather replace it by REPLACEMENT and return the result.

   Examples:

      Get first character:              substr(string,  0, 1)
      Get last character:               substr(string, -1, 1)
      Remove first character:           substr(string,  1)
      Remove last character:            substr(string,  0, -1)
      Remove first and last character:  substr(string,  1, -1)

   SUBSTR is a MATLAB version of the Perl operator with the same name.
   However, unlike Perl's SUBSTR, no warning is produced if the substring
   is totally outside the string.

0001 function outstr = substr(str, offset, len, repl)
0002 %SUBSTR Extract a substring out of a string.
0003 %
0004 %   SUBSTR(STRING, OFFSET, LENGTH) extracts a substring out of STRING with
0005 %   given LENGTH starting at the given OFFSET.  First character is at offset
0006 %   0.  If OFFSET is negative, starts that far from the end of the string.
0007 %   If LENGTH is omitted, returns everything to the end of the string.  If
0008 %   LENGTH is negative, removes that many characters from the end of the
0009 %   string.
0010 %
0011 %   SUBSTR(STRING, OFFSET, LENGTH, REPLACEMENT) will not return the
0012 %   substring as specified by STRING, OFFSET, and LENGTH (see above) but
0013 %   rather replace it by REPLACEMENT and return the result.
0014 %
0015 %   Examples:
0016 %
0017 %      Get first character:              substr(string,  0, 1)
0018 %      Get last character:               substr(string, -1, 1)
0019 %      Remove first character:           substr(string,  1)
0020 %      Remove last character:            substr(string,  0, -1)
0021 %      Remove first and last character:  substr(string,  1, -1)
0022 %
0023 %   SUBSTR is a MATLAB version of the Perl operator with the same name.
0024 %   However, unlike Perl's SUBSTR, no warning is produced if the substring
0025 %   is totally outside the string.
0026 
0027 %   Author:      Peter J. Acklam
0028 %   Time-stamp:  2003-03-31 18:19:53 +0200
0029 %   E-mail:      pjacklam@online.no
0030 %   URL:         http://home.online.no/~pjacklam
0031 
0032    % Check number of input arguments.
0033    error(nargchk(2, 4, nargin));
0034 
0035    n = length(str);
0036 
0037    % Get lower index.
0038    lb = offset + 1;             % offset from beginning of string
0039    if offset < 0
0040       lb = lb + n;              % offset from end of string
0041    end
0042    lb = max(lb, 1);
0043 
0044    % Get upper index.
0045    if nargin == 2               % SUBSTR(STR, OFFSET)
0046       ub = n;
0047    elseif nargin > 2            % SUBSTR(STR, OFFSET, LEN)
0048       if len >= 0
0049          ub = lb + len - 1;
0050       else
0051          ub = n + len;
0052       end
0053       ub = min(ub, n);
0054    end
0055 
0056    % Extract or replace substring.
0057    if nargin < 4
0058       outstr = str(lb : ub);                        % extract substring
0059    else
0060       outstr = [str(1:lb-1) repl str(ub+1:end)];    % replace substring
0061    end